1. Field of the Invention
Aspects of the present invention relate to communication and low noise amplification. More particularly, aspects of the present invention relate to a communication apparatus and a low noise amplifying method, which can reduce a noise figure in a frequency band to be used and can increase circuit integration using a source floor feedback operable at a low voltage in a low noise amplifier structure.
2. Description of the Related Art
The complementary metal-oxide-semiconductor (CMOS) technique is generally used to implement a system-on-a-chip (SoC), because the CMOS technique allows for smaller chips. With smaller chip sizes, better RF performance can be achieved.
Recently, different radio communication standards have emerged, and development of radio communication devices based on the various wireless communication standards is under way. However, usually radio communication devices only support the frequency bands of the wireless communication standards that the device uses. Thus, what is needed is a wireless communication device able to support multiple frequency bands based on a plurality of wireless communication standards so as to support various wireless communication services. Specifically, what is needed is a multiband wireless communication device which can support various frequency bands that are used prevalently, such as WCDMA, CDMA2000, Wibro, Bluetooth, Zigbee, and WLAN, in a single device.
Research and development has recently been conducted on RF-front-end schemes to support multiple frequency bands defined in the plurality of the wireless standards. One of the schemes is a parallel RF-front-end scheme. The parallel RF-front-end scheme employs as many low noise amplifiers (LNAs) and mixers as the number of frequency bands defined in the plurality of the wireless standards supported by the wireless communication device. However, as the device supports more wireless standards, the number of amplifiers and mixers increases, thus increasing the manufacturing cost and the product size of the wireless communication device.
Another scheme for supporting the various frequency bands defined in the plurality of the wireless standards is a reconfigurable mixer scheme. The reconfigurable mixer scheme employs one mixer and a plurality of LNAs to support the plurality of the wireless standards. Disadvantageously, the increased number of LNAs raises the manufacturing cost and increases the product size.